1. Field of the Invention
The present invention relates to a process of the preparation of D(-).alpha.phenylglycine by resolution of DL.alpha.phenylglycine by means of D(+)camphorsulfonic acid in the presence of a strong acid in a reaction vessel, wherein the crystallized salt of the D(-).alpha.phenylglycine is filtrated and then it is subjected to hydrolysis by the addition of a base whereby the D(-).alpha.phenylglycine precipitates and finally said D(-).alpha.phenylglycine is recovered and the obtained filtrate containing the salt of the D(-)camphorsulfonic acid dissolved in water, is introduced again into the reaction vessel, whereas the filtrate, obtained after filtration of the salt of the D(-).alpha.phenylglycine, which filtrate contains L(+).alpha.phenylglycine, is subjected to an alkaline racemization by means of a base, wherein the obtained DL.alpha.phenylglycine is also introduced into the reaction vessel.
2. Brief Description of the Prior Art
The preparation of D(-).alpha.phenylglycine by resolution of a racemic mixture of DL.alpha.phenylglycine into the D and L isomers by means of D(+)camphorsulfonic acid is known.
Also the alkaline racemization of the undesired L isomer in the racemic DL mixture is known.
The known process for the preparation of D(-).alpha.phenylglycine, wherein subsequent to the racemization the mixture is neutralized and filtrated, whereas the solid DL.alpha.phenylglycine is introduced again into the reaction vessel and the filtrate is removed as effluent water, has as disadvantages that together with the filtrate salts, very expensive DL.alpha.phenylglycine and especially D(+)camphorsulfonic acid are discarded, which means, that the known process on the one hand is uneconomical because of the loss of expensive starting materials, which from time to time have to be supplemented and otherwise said process causes pollution of the environment.
An object of the present invention is to eliminate the above mentioned disadvantages efficiently.